The Impact of Tsunamis on the Island of Majorca Induced by North Argelian Seismic Sources

Authors: JOSÉ A. ÁLVAREZ-GÓMEZ, MAITANE OLABARRIETA, MAURICIO GONZÁLEZ, LUÍS OTERO, EMILIO CARREÑO, JOSÉ M. MARTÍNEZ-SOLARES

Abstract: The north of Algeria is the main earthquake-related tsunami generation zone that threatens the Balearic Islands. In this work we review the major seismic series of the area -the 1980 El Asnam and the 2003 Boumerdes-Zemmouri earthquakes– in order to obtain a probable worst characteristic earthquake rupture. We estimate rupture dimensions of 55 km x 16 km, reaching the fault plane a depth of 13 km. The dip and rake have been taken as constants, with values of 50° and 90° respectively, while the strike is adjusted to the local tectonic structure. With these characteristics a magnitude M_w= 7.3 earthquake is obtained for an average slip of 4 metres; these values being reasonable for the seismotectonics of the area. Nine sources along the northern coast of Algeria have been proposed, some of them have been mapped offshore and others that are less known are probable continuations of onshore structures. Based on numerical simulations the tsunami impacts of the nine potential events on Majorca have been studied. Catastrophic tsunamis cannot be triggered from these sources in the Balearic Islands. However, wave elevations up to 2 m can generate flooding in low areas and wave amplifications in bays and harbours that can be damaging, as witnessed in historical events.

Keywords: Mediterranean Sea, Balearic Islands, Majorca, Algeria, tsunamis, seismotectonics

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